Thrombocytopenia induced by high-dose chemotherapy remains a significant clinical problem that limits dose intensification of many chemotherapy agents. In our phase I trial of IL-1alpha, we noted increased megakaryocytes in the bone marrow and an increase in the platelet count after IL-1alpha treatment. We designed the present trial to determine if IL-1alpha could ameliorate the thrombocytopenia induced by chemotherapy. We chose carboplatin to combine with IL-1alpha because it has considerable antitumor activity, but is limited by bone marrow suppression, especially thrombocytopenia. This study has enrolled 27 patients to date. Seven patients were in a control group and received carboplatin alone (800 mg/m2). Ten patients received IL-1alpha at 0.03 mcg/kg and ten received 0.1 mcg/kg IL-1alpha with half the patients receiving IL-1alpha before and half after carboplatin (800 mg/m2). Toxicities observed in this trial were similar to those observed with previous trials of either agent alone. IL-1alpha treatment appears to have lessened the degree of thrombocytopenia in some patients, but this effect has not been consistently observed at the first two dose levels of IL-1alpha. Enrollment of 10 patients at the highest IL-1alpha dose (0.3 micro g/kg) will be completed in the near future. If IL-1alpha treatment lessens the bone marrow suppression of carboplatin, a second part of this study will determine to what extent IL-1alpha can increase the dose intensity of carboplatin.